Target

Function

Mediates ATP-dependent export of organic anions and drugs from the cytoplasm. Hydrolyzes ATP with low efficiency. Human MDR3 is not capable of conferring drug resistance. Mediates the translocation of phosphatidylcholine across the canalicular membrane of the hepatocyte.

Involvement in disease

Defects in ABCB4 are the cause of progressive familial intrahepatic cholestasis type 3 (PFIC3) [MIM:602347]. PFIC3 is an autosomal recessive liver disorder presenting with early onset cholestasis that progresses to cirrhosis and liver failure before adulthood. It is characterized by elevated serum gamma-glutamyltransferase levels.Defects in ABCB4 are a cause of intrahepatic cholestasis of pregnancy (ICP) [MIM:147480]; also known as obstetric cholestasis. ICP is a multifactorial liver disorder of pregnancy. It presents during the second or, more commonly, the third trimestre of pregnancy with intense pruritus which becomes more severe with advancing gestation and cholestasis. Cholestasis results from abnormal biliary transport from the liver into the small intestine. ICP causes fetal distress, spontaneous premature delivery and intrauterine death. ICP patients have spontaneous and progressive disappearance of cholestasis after delivery.Defects in ABCB4 are a cause of gallbladder disease type 1 (GBD1) [MIM:600803]. It is one of the major digestive diseases. Gallstones composed of cholesterol (cholelithiasis) are the common manifestations in western countries. Most people with gallstones, however, remain asymptomatic through their lifetimes.